Propeller manufacturing & material selection.

[nur azizah aziz]

a) How would you manufacture large propellers for ships?
b) Select a suitable material for this application . Explain your selection .

[UsedProp]

Most propellers large and small are manufactured by a sand casting process in which molten metal is poured into a two part mould that is made out of a special casting sand that has been formed around a wooden (most often) pattern of the propeller. Most props are cast in one piece however some may be cast in several sections that “bolt” together. A good example may be a folding sailboat propeller. After the rough casted propeller has cooled the bore will be machined, the blades are checked and trued, ground, polished and balanced. Some propellers are cast extra thick and then machined by a CNC mill resulting in a very accurate machined pitch.

As for the materials used that will depend on the following: strength, durability, availability & cost. Most props are made from Manganese bronze, Nibral (a nickel, bronze, aluminum mix) or stainless steel. Bronze is most often a good choice very durable and low cost. Nibral and stainless are stronger and have a better resistance to electrolysis, they are also more expensive and harder to repair.